What is meant by activated sludge in the context of wastewater treatment?

Activated sludge refers to a mass of microorganisms that are used in the biological treatment process to digest organic matter in wastewater. In this process, wastewater is aerated to promote the growth of these microorganisms, such as bacteria and protozoa, which consume the organic pollutants present in the wastewater. As the microorganisms metabolize the organic material, they convert it into new cellular matter and gases, effectively reducing the levels of harmful pollutants.

This method is integral to secondary treatment processes in wastewater treatment plants, where the primary focus is on reducing biochemical oxygen demand (BOD) and removing suspended solids. The "activated" aspect signifies that these microorganisms are in a suspended state in the aeration tank, actively participating in the breakdown of pollutants. Once the treatment process is completed, the activated sludge can then be separated from treated water, with some of it returned to maintain the microbial population in the system while excess is removed as waste.

Understanding activated sludge is crucial for operators, as it plays a key role in ensuring the efficiency and effectiveness of wastewater treatment processes, contributing to environmental protection and public health.